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This paper presents vehicle occupant body imaging algorithms for detecting the presence of children that are left behind in vehicles. The proposed algorithms utilize occupancy grid mapping (OGM) techniques developed for autonomous driving, which are modified for in-cabin human detection purposes. Two different kinds of OGM techniques are presented to deal with two major difficulties in imaging the occupant bodies in an in-cabin environment. The processing flows of the proposed algorithms are detailed in this report. Two experimental results for 60 GHz millimeter-wave radars are also presented for performance verification.

A space-borne synthetic aperture radar (SAR) is widely used for maritime surveillance because it can observe a broad area. Although a low pulse repetition frequency (PRF) mode is generally selected to observe a wider area, it causes azimuth ambiguities that may lead to false detection and affect the accuracy of ship detection. In previous work, an azimuth ambiguity discrimination algorithm using the Doppler spectrum was presented. However, this algorithm did not eliminate false detection and presented challenges for ship detection performance. To achieve more precise detection, a novel algorithm using a compressive sensing (CS)-based SAR image is proposed. CS can reconstruct the ambiguity-suppressed SAR image, resulting in further improvement of azimuth ambiguity discrimination. The proposed algorithm was applied to a SAR image simulated by half-downsampling of the received signals. The evaluation shows that the proposed algorithm suppresses the power of azimuth ambiguity up to 15 dB and eliminates false detection. These findings demonstrate that the algorithm discriminates robustly and significantly improves ship detection performance.

We propose a novel SAR azimuth ambiguity suppression method. The proposed method is a post process for a SAR image; namely, it does not require any modification to the SAR image formation process nor the SAR system design. Noting that the azimuth ambiguity is blurred in the SAR image, the proposed algorithm refocuses the image to focus the azimuth ambiguity and then automatically detects and identifies the locations, and also the orders, of the ambiguities in the refocused image. After the detected ambiguities in the refocused image are eliminated, the final SAR image is obtained by refocusing back to the true image. Experimental results using true satellite images show that the proposed method successfully suppresses the ambiguities without causing severe degradations to the true images.

Synthetic Aperture Radar (SAR) can take a fine radar image without relation to sunshine condition. Recently, video generated from SAR is discussed. The radar video offers the practical understanding of the target motion without the added implement. The radar video is often generated from raw data in spotlight mode. In contrast, we propose the radar video generated from SAR image. The proposed scheme provides a low complexity and the freedom of the observation mode. In the paper, we show the process of the proposed scheme and indicate the snapshot image of radar video made of our air-borne stripmap SAR data or Advanced Land Observing Satellite-2 data. The images show possibility of the radar video with stripmap mode or space-borne SAR.

Inverse synthetic aperture radar (ISAR) is one of the radar techniques used to observe 2-D images of a remotely based target using radio waves. If we keep observing the target and consecutively generate multiple ISAR images, which we call an ISAR movie, the target image varies considerably due to the motion of the target. The authors have proposed an algorithm for reconstructing a 3-D target shape from an ISAR movie; however, the algorithm requires a priori knowledge of the relative motion of the target. In this paper, we propose a novel method that estimates the relative motion and the 3-D shape of the target using a multistatic ISAR movie.

For urban area monitoring, detection and classification of small targets with synthetic aperture radar imagery are one of the useful solutions. The conventional method has the problem that when a target on both master and slave images at the same position has the same radar cross section, it does not classify the target as either a slightly moved reparked vehicle or as a different vehicle. To overcome this problem, we propose a Fourier-transform-based simple phase compensation method for both accurate coherence estimation and classification of the reparked vehicle's status. The proposed method obtains the maximum value of the frequency basis, and also determines the threshold, which is based on effective sample number, with a constant false alarm rate. This number is determined by the peak signal-to-noise ratio in estimation window, and are used on the preprocessed probability density function for each sample number. Finally, the proposed method classifies a target as either a slightly moved vehicle or as a different vehicle by using both the proposed coherence and threshold detection, which enables it to determine the target status. Experimental results with the COSMO-SkyMed X-band spotlight SAR images demonstrate the effectiveness of the proposed method.

This paper presents an experimental result to demonstrate azimuth ambiguity suppression with the displaced phase center antenna technique that is promising technique to realize the high resolution wide swath imagery for spaceborne synthetic aperture radar (SAR). The dual receiver antenna data was acquired by airborne Ku-band SAR. In this paper, we propose a signal compensation procedure to cope with beam squint for the following coherent signal processing such as the dual channel reconstruction algorithm. The azimuth ambiguity suppression capability is evaluated by comparing the image reconstructed from dual-receiver channel to the single receiver channel image. The experimental result shows significant azimuth ambiguity suppression.

Along track interferometric (ATI) synthetic aperture radar (SAR) has the capability of detecting moving targets and measuring the line-of-sight velocity of the target. With the ATI SAR, the current velocity map can be obtained by combining two perpendicular ATI data sets recorded over sea in rapid succession. In this paper, we describe how sea surface current can be mapped using airborne Ku-band SAR and present results of sea surface current at Cape Irago in Japan.

Synthetic Aperture Radar (SAR) often suffers from interference signal from various radio sources. In general, notch filters or band elimination filters have been utilized to eliminate such interference signal; however, if the bandwidth of the interference signal is relatively wide, the gap in the spectrum caused by the band elimination filter could significantly degrade the original image. We propose an algorithm to suppress relatively wide bandwidth interference while maintaining the image quality. In the algorithm, spatially variant interference suppression filter is generated based on the signal of interference free band, then the filter is applied to the interference contaminated image. Unlike the band elimination filter, the spatially variant interference suppression filter preserves the signal component within the interference contaminated band; therefore, the image distortion caused by the spectrum gap can be largely eliminated. The algorithm has been tested with a simulated interference contaminated image generated from the real 10cm resolution airborne Ku band SAR image and a TerraSAR-X image. It has been shown that while conventional band elimination filter would degrade the image quality, the image quality of the interference suppressed image obtained by the proposed algorithm is satisfactory.

Inverse synthetic aperture radar (ISAR) is one of the radar techniques used to observe two-dimensional images of a remotely based target using radio waves. If we keep observing the target and consecutively generate multiple ISAR images, which we call ISAR movie, the target image varies considerably due to the motion of the target. The authors have proposed an algorithm for reconstructing three dimensional target shape from an ISAR movie; however, the algorithm requires a priori knowledge of the relative motion of the target. In this paper, we propose a novel method that estimates the relative motion and the three dimensional shape of the target using multistatic ISAR movie.

Synthetic aperture radar (SAR) images are very useful for many applications. However, SAR images require a great deal of experience for the interpretation, since the appearances are very different from optical images. Additionally, the appearances change significantly by the observational condition, such as frequency and incident angle. We propose a SAR image simulating algorithm developed for the aid of the SAR image analysis and training. The simulator is also intended to support the SAR system configuration design by providing the expected images. The main features of the algorithm are the capability of wide area simulation and the low computational costs. The simulated image of 10 km square area is shown and compared with the real image